It is possible to explicitly record different styles of speech and
different prosodic contexts. For example we build a databases from a
smaller 500 utterance prompt list where every second word was read
with emphasis. For example from a database recorded as this

Then each segment in each emphasized word is marked with an emphasis
feature. During synthesis each word desired to have emphasis is
constructed from the only those segment with that emphasis feature.
We can synthesize emphasized examples like this